Temple Run 2 is off to a running start this weekend, logging more than 20 million downloads in its first four days of availability on Apple's App Store.

The sequel to the popular endless action video game became the top free app just eight hours after its release, according to developer Imangi Studios. The iOS game, in which runners try to escape a giant, evil monkey, is also the No. 3 top-grossing app, thanks to in-app purchases that boost characters' skills and improve their chances of running a personal best distance.

"The response from fans has been overwhelming," Keith Shepherd, co-founder of Imangi, said in a statement today. "We are thrilled players want more of the Temple Run universe, and we hope to grow and expand the game over the coming months."

The original Temple Run was downloaded more than 170 million times on Apple's App Store, Google Play, and Amazon Marketplace, the company said.